Analysis of quinolone-resistance in commensal and diarrheagenic escherichia coli isolates from infants in lima, Peru

Background: Antibiotic resistance is an increasing problem, particularly in countries where antibiotic use is frequently not controlled. The aim of this study was to analyse the prevalence of the molecular mechanisms of quinolone-resistance in E. coli isolated from faeces of healthy Peruvian children or those presenting diarrhoea. Methods: The presence of target mutations, transferable quinolone-resistance mechanisms and the role of Phe-Arg-b-Naphtylamyde inhibitible efflux pumps were studied in 96 Escherichia coli (46 diarrheogenic and 50 non-diarrheogenic) isolates exhibiting resistance or diminished susceptibility to quinolones. Results: The most resistant phenotype, Nal^R and Cip^R, was most frequently present in isolates of healthy children. The distribution of quinolone resistance mechanisms between diarrheogenic (DEC) and commensal (non DEC) isolates was equitable, although the aac(6')Ib-cr gene was mainly detected in DEC isolates: 17 (34%) vs non DEC isolates nine (20%). QnrB was present in five (10%) DEC vs three (6%) non DEC isolates. Conclusions: Point mutations in gyrA and parC genes play a relevant role in quinolone resistance acquisition and highlight the role of efflux pumps also. This study provides knowledge about the molecular mechanisms involved in quinolone resistance in isolates in a non exposed population under high community antibiotic pressure.